Large hauling vehicles such as those used for highway construction and mining operations, typically utilize a fabricated axle construction. The axle generally includes an axle housing to which wheel spindles are rigidly attached. The axle housing is coupled to the vehicle frame utilizing suspension struts on a trailing side of the housing. The leading or forward side of the housing may be coupled to the frame via a suspension arm including a pivot connection.
To reduce weight without sacrificing strength, some axle housings are fabricated as a weldment. For example, in an axle of the type that utilizes electric traction motors, the wheels spindles are attached to a fabricated, cylindrical shaped housing member. The traction motors for the wheels are typically enclosed within the housing member.
When fully loaded, a significant, predominantly bending load is applied to the axle housing member. In particular, a substantial portion of the vehicle's weight is borne by the rear wheels, which are rotatably attached to the spindles. The spindles are typically bolted to the sides of the axle housing. Under load, the wheels generate a bending load on the spindles. The spindles in turn transfer this bending load to the axle housing. As a result of this bending load, the upper portion of the axle housing is under a compressive load whereas the lower portion of the housing is under substantial tension.
It has been found that large loads applied to the housing especially when the vehicle is overloaded, can produce premature fractures or other failures in the housing. It is believed that these failures are primarily due to the tension force that is applied to the lower portion of the wheel motor housing by the spindles.